Problem: Solve for $x$ and $y$ using substitution. ${6x-y = -10}$ ${y = -x-11}$
Solution: Since $y$ has already been solved for, substitute $-x-11$ for $y$ in the first equation. ${6x - }{(-x-11)}{= -10}$ Simplify and solve for $x$ $6x+x + 11 = -10$ $7x+11 = -10$ $7x+11{-11} = -10{-11}$ $7x = -21$ $\dfrac{7x}{{7}} = \dfrac{-21}{{7}}$ ${x = -3}$ Now that you know ${x = -3}$ , plug it back into $\thinspace {y = -x-11}\thinspace$ to find $y$ ${y = -}{(-3)}{ - 11}$ $y = 3 - 11$ $y = -8$ You can also plug ${x = -3}$ into $\thinspace {6x-y = -10}\thinspace$ and get the same answer for $y$ : ${6}{(-3)}{ - y = -10}$ ${y = -8}$